JP2015077740A - Composite material and manufacturing method of composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite material which is provided with vibration characteristics having anisotropy equivalent to natural wood and has high processability, and to provide a manufacturing method of the composite material.SOLUTION: A composite material includes with a part of lignin removed therefrom which retains orientation of fiber, and resin with which the wood is impregnated. The lignin may be removed at least on the surface of the wood. The manufacturing method of the composite material includes steps of: digesting the wood while the orientation of fiber is retained; impregnating the digested wood with the resin; curing the resin while compressing the wood impregnated with the resin. It is preferable that a lignin content in the wood is in the range of 5 to 15 mass%. A volume compression rate of the wood in the step of curing the resin is preferably 90% or less.

Description

  The present invention relates to a composite material and a composite material manufacturing method.

  Wood has long been used for various purposes, and is also widely used as an acoustic material for woodwind instruments, stringed instrument bodies, piano soundboards, speaker diaphragms, and the like. In some musical instruments and the like, it is considered that the anisotropy of vibration characteristics of natural wood contributes to the sound quality, and natural wood is preferred as the material. However, natural wood is susceptible to cracking along the fibers due to defects such as voids and voids between the fibers. For this reason, musical instruments that use natural wood may be expensive due to poor yields during processing.

  Therefore, in order to make it easy to bend the wood, a method is known in which the wood is heated with steam, an alkaline solution, or the like (see JP-A-6-178386). Further, a composite material may be obtained by impregnating wood with a resin. As a specific example, there has been proposed a loudspeaker diaphragm formed by heat-pressing wood that has been given moisture, drying, impregnating a resin, and curing (see Japanese Patent Application Laid-Open No. 2004-266695). In addition, a musical instrument material in which a thin plate of natural wood is coated or impregnated with a resin and laminated and bonded has been proposed (see JP 2007-196692 A).

  By the way, natural wood is mainly composed of fibrous cellulose and hemicellulose and lignin, which is a resin that joins them together. When natural wood is wet-heated with steam or an alkaline solution, lignin that binds the fibers in the wood is eluted. This technique is called cooking, and is widely used as a technique for removing fibers in wood as a so-called pulp by removing lignin.

  Therefore, when natural wood is heated with an aqueous solution, particularly an alkaline solution, lignin is eluted and is likely to break along the fiber. For this reason, in Japanese Patent Application Laid-Open No. 2004-266695, wood is immersed in an aqueous solution in which saccharides are dissolved instead of mere water or an alkaline aqueous solution, and is subjected to hot press molding. However, even when heated using an aqueous solution in which saccharides are dissolved, elution of lignin from wood cannot be completely prevented. For example, when wood machinability is more important, such as woodwind instruments. It is insufficient as a countermeasure against cracking.

JP-A-6-178386 JP 2004-266695 A JP 2007-196692 A

  In view of the above circumstances, it is an object of the present invention to provide a composite material and a composite material manufacturing method having vibration characteristics having anisotropy equivalent to that of natural wood and high workability.

  The invention made in order to solve the above-mentioned problems is a composite material comprising a wood from which a part of lignin has been removed and the orientation of fibers maintained, and a resin impregnated in the wood.

  Since a part of the lignin is removed from the wood, the composite material can be easily formed into a desired shape in the manufacturing process. In addition, since the composite material impregnates the gaps and pipes of fibers formed by removing lignin from wood, the composite material is hard to break even by cutting, and has an excellent surface or cut surface aesthetics. Furthermore, since the composite material retains the fiber orientation, it retains the anisotropy of the physical properties of the raw material wood, and has vibration characteristics having anisotropy similar to that of natural wood. For this reason, the said composite material can be utilized as a material which substitutes for natural wood.

  The composite material only needs to have lignin removed on at least the surface of the wood. By removing the lignin on the surface of the wood, the surface of the wood is impregnated with the resin, and the characteristics of the material surface that is particularly susceptible to the performance of the acoustic material can be improved.

  Further, another invention made to solve the above-mentioned problems includes a step of digesting wood so as to maintain fiber orientation, a step of impregnating the digested wood with a resin, and the wood impregnated with the resin And a step of curing the resin in a compressed state.

  In the composite material manufacturing method, wood is digested to remove a part of lignin, so that it can be formed into a desired shape before the resin is cured. Further, in the composite material manufacturing method, since the resin impregnates the gaps and the pipes of the fibers formed by removing the lignin of the wood, it is difficult to break even if it is cut, and the composite is excellent in the appearance of the surface or the cut surface. Material can be manufactured. Further, in the composite material manufacturing method, the orientation of the fiber is maintained even after cooking, and thus the composite material obtained has vibration characteristics having anisotropy similar to natural wood. For this reason, the composite material manufactured by the said composite material manufacturing method can be utilized as a material which substitutes for natural wood. In addition, in the composite material manufacturing method, since the resin is cured in a state where the wood is compressed, the density of the fibers is high, the vibration characteristics of the raw material wood are highlighted, and a composite material with higher strength can be manufactured.

  In the composite material manufacturing method, the lignin content in the digested wood is preferably 5% or more and 15% or less. Thereby, sufficient cracking difficulty can be provided by resin impregnating the gap of the fiber after removing lignin, maintaining the orientation of the fiber.

  The volume compressibility of the wood in the step of curing the resin is preferably 90% or less. As a result, a composite material having anisotropic vibration characteristics similar to that of wood and having high strength and workability can be manufactured.

  The composite material according to the present invention retains the fiber orientation, and the resin is impregnated in the gaps between the fibers from which the lignin has been removed. There are few cracks at the time, and workability is improved. For this reason, the said composite material can be utilized suitably as a material which substitutes for natural wood.

It is a flowchart which shows the composite material manufacturing method of one Embodiment of this invention. It is the photograph which expands and shows the surface of raw material wood. It is the photograph which expands and shows the surface of the digested wood. It is a photograph which shows a mode that external force was added to the timber of FIG. It is a figure which shows the cutting shape of the timber for forming the diaphragm for speakers of one Embodiment of this invention. It is a figure which shows the cutting shape of the timber for forming the diaphragm for speakers of embodiment different from FIG. It is a photograph which shows the composite material of Example 1 of this invention. It is a photograph which shows the cross section of the composite material of FIG. It is a photograph which shows the composite material of Example 2 of this invention. It is a photograph which shows a tapping test apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[Composite material manufacturing method]
The composite material manufacturing method shown in FIG. 1 includes a step of digesting wood (step S1), a step of rinsing wood (step S2), a step of drying wood (step S3), and a step of cutting wood (step S4). ), A step of laminating wood (step S5), a step of impregnating wood with resin (step S6), and a step of hardening the resin in a compressed state of wood (step S7).

<Wood>
The wood used in the composite material manufacturing method is not particularly limited, but an optimum material is selected according to the vibration characteristics required for the target composite material, and it may be hardwood or softwood. Good. The composite material manufacturing method can also be applied to the case where wood used in the manufacture of a specific musical instrument is used as a raw material and is made into a composite material in order to improve its workability, and spruce, granadilla, etc. are used as raw material wood. Good. Moreover, you may manufacture the composite material which can substitute expensive wood from the cheap wood by the said composite material manufacturing method.

  It is preferable that the wood used as a raw material is cut into a predetermined size so that the degree of cooking is constant. The width and length of the wood are determined to be large enough to obtain the target composite material within the constraints of the size of the digester.

  As a minimum of the thickness of wood, 0.3 mm is preferred and 0.5 mm is more preferred. On the other hand, the upper limit of the thickness of the wood is preferably 10 mm, and more preferably 5 mm. If the thickness of the wood is less than the lower limit, the wood is easily damaged during the work, and the production efficiency may be reduced. Moreover, when the thickness of the wood exceeds the upper limit, the progress of cooking between the surface and the center of the wood is different, and it may be difficult to form a homogeneous composite material.

  However, by deliberately delaying the cooking of the center part by using thick wood, the degree of cooking (content of lignin after cooking) differs between the wood surface and the center of gravity. You may change the composition of the composite material obtained. For example, when a woodwind instrument material is used, the strength of the outer surface of the woodwind may be increased while the machinability inside the woodwind is enhanced.

<Cooking process>
In the composite material manufacturing method, first, in step S1, wood as a raw material is digested, and a part of lignin is removed while maintaining the fiber orientation in the wood. This cooking can be efficiently performed by heating the raw material wood immersed in an alkaline solution.

  Specifically, the alkaline solution and the wood are steam-heated by immersing wood in an alkaline solution stored in a container having alkali resistance and heat resistance, and placing the wood inside the pressure steam kettle together with the container. A plurality of pieces of wood may be immersed in one container, and a net, a basket, etc. for taking in and out the wood may be used. The size of the container is preferably selected according to the volume of the wood to be immersed so that the alkaline waste liquid can be reduced.

  As the alkaline solution, for example, an aqueous sodium hydroxide solution can be used. Further, the alkaline solution may contain an auxiliary such as anthraquinone and other additives. The amount of the alkaline solution used is such that the wood can be completely immersed.

  As a minimum of sodium hydroxide mass conversion value of the amount of alkali addition to wood mass, 10% is preferred and 15% is more preferred. Moreover, as an upper limit of the said alkali addition amount, 45% is preferable and 40% is more preferable. If the amount of alkali added is less than the lower limit, it is necessary to increase the cooking temperature or lengthen the cooking time, so that lignin may not be sufficiently eluted. On the other hand, if the amount of alkali added exceeds the upper limit, the reaction is too fast and it may be difficult to cook evenly into the wood.

  The cooking temperature depends on the amount of alkali added, but the lower limit is preferably 120 ° C., more preferably 150 ° C. Moreover, as an upper limit of cooking temperature, 200 degreeC is preferable and 180 degreeC is more preferable. If the cooking temperature is less than the lower limit, the reaction rate is slow, and it may take time for cooking. In addition, if the cooking temperature exceeds the upper limit, the equipment is required to have high pressure resistance, and the cost becomes excessive.

  The cooking time is determined according to the amount of alkali added and the cooking temperature, and the lower limit thereof is preferably 15 minutes, more preferably 30 minutes. Moreover, as an upper limit of cooking time, 5 hours are preferable and 3 hours are more preferable. If the cooking time is less than the lower limit, it may be difficult to cook the surface and center of the material evenly. Moreover, when cooking time exceeds the said upper limit, there exists a possibility that manufacturing cost may become excessive.

  However, when the degree of cooking differs between the surface and the center of the wood, it may be preferable that the amount of alkali added, the cooking temperature, and the cooking time be different from the aforementioned ranges.

  In this cooking step, a part of lignin is removed while maintaining the orientation of the fibers of the wood from the surface of the wood toward the center. In the wood after cooking, since the amount of lignin around the fibers is reduced, the fibers are weakly bonded to each other by remaining lignin or hydrogen bonds. For this reason, the wood after cooking is easy to bend in the direction perpendicular to the orientation direction of the fibers so that the distance between the fibers is changed little by little compared with the natural wood before cooking. In addition, in the wood after cooking, the rigidity of the fiber itself is reduced due to a decrease in lignin. For this reason, the wood after cooking is easier to bend in the direction in which the fibers are bent than the natural wood before cooking. In view of these actions, the lignin content of the wood after cooking can be used as a specific numerical index for the ease of deformation and bending of the wood after cooking.

  The lower limit of the lignin content of the evenly digested wood is preferably 5% by mass, more preferably 8% by mass. On the other hand, the upper limit of the lignin content of the wood after cooking is preferably 15% by mass, and more preferably 12% by mass. If the lignin content after cooking is less than the lower limit, the remaining lignin cannot sufficiently join the fibers, and the fibers may be disaggregated. On the other hand, if the lignin content after cooking exceeds the upper limit, the bonding strength between the fibers is too high, the bending workability may be insufficient, or the resin may not be sufficiently impregnated in the subsequent process.

  FIG. 2 shows an enlarged photograph of the wood surface before cooking. Wood fibers form a canal through which water and nutrients flow along the trunk and branches of the tree. These fibers are composed mainly of cellulose of fibers and bonded with short fibers of hemicellulose and resin lignin. The wood in FIG. 2 is spruce, and a wall hole (a hole for flowing water and nutrients in a direction crossing the fibers) is opened in each canal. Adjacent fibers (tracheal ducts) are joined together by lignin, and the binding force is very strong. For this reason, when natural wood breaks along the fiber, the pipes joined by lignin are not separated from each other, but the pipes are torn and divided into two along the fiber direction.

  Furthermore, the photograph which expanded the wood surface after cooking in FIG. 3 is shown. The elution of lignin weakens the junction between the ducts, and in FIG. 3, a gap is partially formed between the conduits. In the wood after cooking, the orientation of the fibers is maintained by hydrogen bonds between the fibers in addition to the remaining lignin. When a large force is applied to the wood after cooking, the remaining lignin or fibers bonded by hydrogen bonding are separated from each other, so that the canal can be disassembled as shown in the photograph of FIG. In FIG. 4, the fibers are disassembled into pieces for easy understanding. However, when moderate bending stress is applied, the wood is bent and deformed by causing a slight shift between the fibers while maintaining the fiber arrangement roughly. Be made.

<Rinsing process>
In the composite material manufacturing method, subsequently, in step S2, the digested wood is rinsed to wash away the alkaline solution. Specifically, the step of discharging the alkaline solution from the container in which the wood is dipped, pouring clean water instead, leaving it for a while and then draining it is repeated. Since the alkaline solution after cooking is black, this process is repeated until the color of newly poured water does not change. The pH may be measured to check the remaining amount of alkali.

<Drying process>
Next, in step S3, the wood that has been rinsed after cooking is dried. This drying may be performed in a high temperature environment in order to shorten the time. In that case, it is good to dry in the state which piled and pressed the several timber so that a crack and deformation | transformation may not arise in timber by rapid drying.

<Cutting process>
In step S4, the dried wood is trimmed according to the length and width of the composite material to be finally obtained. The wood that has undergone the cooking step, the rinsing step, and the drying step shrinks slightly smaller than the original size, and can be greatly compressed during drying, particularly in the thickness direction. Further, since the shrinkage rate is not constant due to variations in raw materials, in this step S4, the wood is trimmed again to a predetermined size.

<Lamination process>
In step S5, the thickness required for the composite material to be obtained is formed by laminating cut and trimmed thin wood. However, it is set as the thickness which considered the compression rate in the compression and resin hardening process mentioned later. At this time, it is possible to form a composite material having vibration characteristics close to those of natural wood by laminating the fibers in the same direction. Further, if necessary, vibration characteristics that are not found in natural wood can be imparted by changing the direction of the fibers of the wood and laminating. Further, by laminating the wood before impregnating the resin, it is possible to prevent an air layer from being left between the woods.

<Resin impregnation process>
In step S6, the laminated wood is impregnated with resin. Since these timbers have gaps formed by removing lignin in step S1, resin is easily impregnated in the gaps between the canals and fibers. In particular, if the lignin of the whole wood is evenly and sufficiently removed, the whole wood can be uniformly impregnated with the resin. The resin to be impregnated preferably has a low viscosity when impregnated and is easily cured. For this reason, as the resin to be impregnated, a thermosetting resin is preferable, and a low-viscosity epoxy resin or a polyester resin is preferable. Moreover, it is preferable that this impregnation process is performed under reduced pressure to discharge air in the wood and allow the resin to penetrate into the wood. Moreover, the amount of resin used can be reduced by impregnating the resin with a container shaped to match the wood laminate.

<Compression and resin curing process>
In step S7, the resin is cured in a state where the laminated body of wood impregnated with the resin is compressed in the laminating direction. By compressing the wood here, excess resin is discharged to bring the wood into close contact with each other, and by increasing the fiber density (number per unit cross-sectional area) compared to natural wood, vibration characteristics due to fiber orientation Is remarkably expressed. At this time, since the resin exudes from the wood, the wood laminate and the jig for compressing the wood are bonded by the exuded resin, or the adjacent laminated wood laminates are bonded to each other. In order to prevent this, it is recommended to cover the laminated body of wood with a release film.

  The lower limit of the volume compression ratio of the wood in this compression and resin curing step, that is, the ratio of the volume of the wood before and after compression to the volume of the wood laminated in step S5 is preferably 30%, more preferably 50%, and 70%. Further preferred. On the other hand, the upper limit of the volume compressibility of wood is preferably 90%, more preferably 85%. If the volumetric compressibility of wood is less than the lower limit, the density of fibers in the composite material becomes low, and vibration characteristics having sufficient anisotropy as in natural wood may not be realized. Moreover, when the volume compressibility of wood exceeds the upper limit, the density of fibers in the composite material is too high, and there is a possibility that vibration characteristics different from that of natural wood may be obtained.

  In addition, since the lignin is removed in step S1 and the strength of each fiber and the bonding strength between the fibers are weakened in these woods, a molding strain (residual strain) that generates a residual stress in this compression and resin curing process. Generation is suppressed.

  Furthermore, as a minimum of content of the timber in the composite material finally obtained, 30 mass% is preferable and 40 mass% is more preferable. On the other hand, the upper limit of the content of wood in the composite material is preferably 70% by mass, more preferably 60% by mass, and even more preferably 50% by mass. If the wood content is less than the lower limit, vibration characteristics having sufficient anisotropy like natural wood may not be obtained. On the other hand, if the wood content exceeds the above upper limit, the resin may be insufficient and the fibers in the wood may not be sufficiently bonded, and the strength may be insufficient.

  In step S7, the resin is cured in a state where the wood is compressed as described above. The method of curing the resin is determined according to the type of resin, but when a thermosetting resin is used, it is performed by heating. The heating temperature and the heating time are appropriately determined according to the type of resin, available equipment, the size of the composite material to be manufactured, and the like.

[Composite material]
The composite material manufactured by the manufacturing method of FIG. 1 includes wood from which part of lignin has been removed and fiber orientation and resin impregnated in the wood. In addition, the preferable but not essential configuration of the composite material is obvious from the above description of the manufacturing method.

<Speaker diaphragm>
One embodiment of the composite material manufactured by the composite material manufacturing method can be suitably used as a speaker diaphragm as it is. In the cutting step, the speaker diaphragm is cut in the shape of the truncated cone surface in the cutting step, as shown in FIG. 5, impregnated with resin in the resin impregnation step, and then in the compression and resin curing step. It is formed in a truncated cone shape by being placed between the truncated cone shaped molds and heated in a compressed state to cure the resin. This speaker diaphragm is manufactured without laminating a plurality of woods 10. Also. In this speaker diaphragm, the laminated portions 11 of the wood 10 are joined together by a resin impregnated in the wood 10. Further, the fibers 12 of the wood 10 are oriented in the direction shown in the figure.

  Further, as shown in FIG. 6, one speaker diaphragm may be formed by joining the bonded portions 21 at both ends of two pieces of wood 20 cut into a fan shape. When the elliptical fan-shaped wood 20 shown in FIG. 6 is used, an elliptical speaker diaphragm is formed. As shown in the figure, the wood 20 has the fibers 22 oriented in the major axis direction. That is, the speaker diaphragm formed by laminating the wood 20 has different vibration transmission characteristics in the minor axis direction and the major axis direction.

  The number of wood and the direction of the fibers forming the speaker diaphragm can be arbitrarily selected. Further, one speaker diaphragm may be formed by laminating two or more pieces of wood and curing the resin impregnated in the laminated wood. Further, it is desirable that the speaker diaphragm is light. Therefore, an aqueous emulsion may be included in the resin impregnated in the wood. If an aqueous emulsion is used, the water | moisture content of the aqueous emulsion impregnated at the laminated | stacked wood will evaporate in a compression and resin hardening process of step S7, and a void | hole will be formed there. As a result, a light speaker diaphragm can be obtained while being impregnated with resin.

<Tubular material>
Furthermore, using a mold set having a split cylindrical outer mold and a columnar core, the wood impregnated with resin is wrapped around the columnar core, and the resin is cured in a compressed state with the outer mold. For example, a cylindrical composite material can be formed. In this case, it is preferable that the wood is curved in a direction perpendicular to the fiber orientation direction, that is, in the obtained cylindrical composite material molded body, the wood fibers are oriented parallel to the central axis.

<Advantages>
The composite material manufactured by the composite material manufacturing method includes fibers having an orientation characteristic of wood, and the fibers are bonded with a resin. Due to the action of this resin, the composite material does not easily break along the fiber like natural wood, and therefore has excellent processability. In addition, since the composite material includes fibers having orientation properties, the composite material can have vibration characteristics similar to those of natural wood. For this reason, the said composite material can be utilized as an acoustic material which substitutes the natural wood currently used for the audio equipment, and it enables provision of an inexpensive and homogeneous audio equipment. Also, in the composite material manufacturing method, processability and vibration characteristics can be adjusted by the degree of cooking, the amount of resin impregnation, the compressibility of wood, etc. Can be provided.

[Other Embodiments]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configuration of the above-described embodiment, but is defined by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. Is done.

  In the composite material manufacturing method, a block-shaped wood having a large thickness may be used without being laminated. In this case, the surface of the block-like wood is digested, but the inside is solid wood. Specifically, the composite material using block-like wood is digested so that the lignin content is small on the outer surface and the lignin content increases toward the inside. When the digested wood is impregnated with resin in this way, the amount of resin impregnation is large on the outer surface, and the amount of resin impregnation is small on the inside. Depending on the conditions, the center of the composite material is not impregnated with resin. As described above, those in which the contents of lignin and resin are not constant are also included in the scope of the present invention.

  When only the surface of the wood is digested, the lignin content on the digested wood surface is preferably in the same range as the preferred lignin content in the case of digesting the whole lamellar wood. Specifically, the lower limit of the lignin content on the wood surface after cooking is preferably 5% by mass, more preferably 8% by mass. On the other hand, the upper limit of the lignin content on the wood surface after cooking is preferably 15% by mass, more preferably 12% by mass. It is also preferred that the surface be cooked evenly so that the entire surface of the wood has a uniform lignin content.

  The block-shaped wood means a material that is thick enough not to be digested as a whole, and includes a spherical shape, a conical shape, a cylindrical shape, a prismatic shape, and the like. When using wood having such a shape, in the compression and resin curing process in step S7, the resin-impregnated wood is compressed using a mold or the like, so that unnecessary resin is leached and the fiber density is reduced. Can be big. Thus, by removing lignin on at least the surface of wood and impregnating with resin, an acoustic material having both surface characteristics excellent in acoustic effect and characteristics of wood itself can be obtained. Specifically, a piano soundboard, a guitar soundboard, a speaker diaphragm, a speaker housing, and the like can be considered. In addition, since the resin-impregnated surface looks beautiful, it can be used as a design material for furniture and interior.

  Thus, the composite material formed by removing the lignin on the surface of the wood can be suitably used for producing a woodwind instrument or the like by hollowing out the central portion from which the lignin has not been removed. In this way, only the surface layer of wood is digested and impregnated with resin, leaving the inside of the raw wood as it is, and forming a composite material that improves the vibration characteristics of the surface part that has a particularly large effect on the acoustic effect it can. In addition, the composite material whose surface is reinforced with resin in this way can also suppress cracking when the interior is hollowed out. Further, since the amount of the resin used can be reduced by impregnating the resin only on the surface of the wood as described above, a composite material having excellent vibration characteristics and high workability can be provided at low cost.

  Further, in the composite material manufacturing method, a single sheet-like wood from which lignin has been uniformly removed to the inside is used without being laminated, and a plate-like or sheet-like composite material uniformly impregnated with resin is produced. You can also

  Moreover, in the said composite material manufacturing method, you may replace the order of a resin impregnation process and a lamination process. That is, after impregnating each plate material with the resin individually, the plate material impregnated with the resin may be laminated, and the impregnated resin may be cured in a compressed state.

  Further, in the compression and resin curing step of the composite material manufacturing method, the wood may be deformed into a desired shape by compressing the wood with a mating die having a desired shape. Thereby, the composite material of a desired shape can be manufactured.

  EXAMPLES Hereinafter, although this invention is explained in full detail based on an Example, this invention is not interpreted limitedly based on description of this Example.

[Example 1]
The composite material of Example 1 shown in FIG. 7 was manufactured according to the manufacturing method of FIG. Detailed manufacturing conditions of this prismatic composite material will be described below.

<Wood>
The wood used as the raw material of the composite material in FIG. 7 is a plurality of wood made of spruce and cut into a thin plate shape of length 232 mm × width 42 mm × thickness 2 mm.

<Cooking process>
The alkaline solution used in the cooking was prepared by adding 19.6 g of water necessary for immersing the plurality of raw material wood having a total mass of 227.5 g, 79.6 g of sodium hydroxide corresponding to 35% of the mass of the raw material wood, It is obtained by dissolving 0.273 g of anthraquinone corresponding to 0.12% of the mass of the raw material wood.

  The cooking was performed using a steam kettle, the cooking temperature was 170 ° C., and the cooking time (time for maintaining the cooking temperature) was 1 hour. The time required for temperature increase was 5 minutes, and the time required for cooling was 3 minutes.

<Rinsing process>
In the digested wood, the alkaline solution was removed to such an extent that the color of the immersed water did not change by repeating the immersion for about 2 hours and the exchange of water eight times.

<Drying process>
The well-rinsed and dealkalized wood was sufficiently dried by leaving it in a drying chamber at about 120 ° C. in a state of being laminated and pressed in order to prevent cracking and warping. The dried wood was compressed from 1 mm to 1.2 mm in thickness.

<Cutting process>
The dried wood was trimmed to a length of 110 mm and a width of 35 mm.

<Lamination process>
30 pieces of the dried wood were laminated. The height of the laminate in the stacking direction was 35 mm, and the total weight was 62.9 g.

<Resin impregnation step>

  The laminate of wood was put in a polyethylene bag, and the epoxy resin was poured therein. This was placed in a vacuum dryer and decompressed at 60 ° C. for 1 hour to degas the wood and impregnate the resin.

  The epoxy resin used is "Araldite LY1564 (trademark)" manufactured by Huntsman Advanced Materials, and "Fujicure 7000 (trademark)" manufactured by T & K TOKA Corporation is used as a curing agent. And 1.5 parts by mass of an auxiliary agent are mixed.

<Compression and resin curing process>
The laminate of wood impregnated with resin was wrapped in a release film, sandwiched between aluminum plates, and compressed in the stacking direction with a vise. The 30 wood laminates were compressed to a height of 28.3 mm, and the volume compression ratio was about 81%.

  Thus, the laminated body of the wood compressed in a vise was put into an oven, and the epoxy resin impregnated in the wood was cured by heating at 120 ° C. for 16 hours and further at 180 ° C. for 1.5 hours. .

  The composite material of FIG. 7 manufactured in this way has a length (lateral length in the illustrated direction) 110 mm × width (depth of the upper surface in the illustrated direction) 35 mm × height (vertical height in the illustrated direction) C) 28.3 mm. This composite material is formed by stacking 30 pieces of wood in the height direction.

  The mass of the prismatic composite material was 146.5 g, and the ratio of the wood in the composite material calculated as the ratio of the mass of the wood before impregnation with the resin was 43%.

  FIG. 8 shows a cut surface obtained by cutting the end of the prismatic composite material of FIG. 7 perpendicularly to the length direction. In the figure, wood is stacked in the vertical direction. An annual ring can be confirmed in each layer of the raw material wood, and a line inclined with respect to the stacking direction of the plate material visible on the cut surface is a cut mark by the saw.

  By this cutting, it was confirmed that the composite material of Example 1 had the same machinability as wood, and that no cracks were easily generated.

[Example 2]
Moreover, according to the manufacturing method of FIG. 1, the composite material of Example 2 shown in FIG. 8 was manufactured. This plate-like composite material was manufactured under the same conditions except that the prismatic composite material of FIG. 7 was different in size and number of layers. However, the plate-shaped composite material of FIG. 9 is slightly different from the prism-shaped composite material of FIG. Only the differences between the plate-shaped composite material of FIG. 9 and the prismatic composite material of FIG. 7 will be described below, and redundant description will be omitted.

  The plate-shaped composite material of FIG. 9 has a length of about 230 mm × a width of about 35 mm × a height (thickness) of 6 mm and a weight of 74.7 g. For this reason, in the cutting step, the wood was cut into a length of 230 mm and a width of 35 mm. Further, the plate-shaped composite material of FIG. 9 was obtained by laminating seven pieces of wood, and the wood laminate before impregnating the resin had a height of 8 mm and a total weight of 30.7 g. Therefore, the volume compressibility in the production of the plate-shaped composite material of FIG. 9 was 75%, and the content of wood in the plate-shaped composite material of FIG. 9 was 41 mass%.

  And about the plate-shaped composite material of FIG. 9, the vibration characteristic was confirmed using the tapping test apparatus shown in FIG. This tapping test apparatus confirms transmission of vibration by hitting one end (right end in the figure) of a plate-shaped composite material with a hammer and monitoring the vibration. By performing mode analysis on the data measured using this tapping test device, the sound speed, loss coefficient (tan δ), etc. in the plate material are derived, but since the mode analysis of the vibration phenomenon is a known method, its detailed Description of the procedure is omitted. Suitability as an acoustic material for a specific application can be determined particularly by whether or not the loss coefficient (tan δ) in the primary vibration mode is within a predetermined range.

The plate-shaped composite material of FIG. 9 is a prototype manufactured as an alternative material for Granadilla. A typical loss factor in the primary vibration mode of Granadilla is 7 × 10 ⁻³ , and this value is set as a target value for the prototype composite material. The loss factor in the primary vibration mode of the plate-shaped composite material of FIG. 9 and another composite material manufactured under the same conditions together with the composite material of FIG. 9 was 7.5 × 10 ⁻³ and 8 × 10 ^−3. It was. The loss coefficient in the primary vibration mode of the composite material is allowed if the difference from the target value is ± 2 × 10 ⁻³ . Thus, these composite embodiments can be used satisfactorily as an alternative to Granadilla.

  The composite material manufacturing method and the composite material can be widely applied to provide a material that replaces natural wood. The composite material can be suitably used as an acoustic material, but can also be used as a design material that makes use of a surface smoothed by a resin.

10, 20 Wood 11, 21 Laminated parts 12, 22 Fiber S1 Cooking step S2 Rinse step S3 Drying step S4 Cutting step S5 Lamination step S6 Resin impregnation step S7 Compression and resin curing step

Claims (5)

  A composite material comprising wood from which part of lignin has been removed and retaining fiber orientation, and a resin impregnated in the wood.   The composite material according to claim 1, wherein lignin is removed on at least a surface of the wood. Cooking the wood to maintain fiber orientation;
Impregnating the digested wood with resin;
And a step of curing the resin in a compressed state of the wood impregnated with the resin.   The method for producing a composite material according to claim 3, wherein the lignin content in the digested wood is 5% by mass or more and 15% by mass or less.   The composite material manufacturing method according to claim 3 or 4, wherein the volume compression ratio of the wood in the step of curing the resin is 90% or less.